(a) Field of the Invention
The invention relates to a transformer for cathode tube inverter, and more particularly, to a twin-like U-shaped or a triplet-like transformer, wherein a primary coil thereof is shared, the primary coil and other secondary coils thereof are completed isolated with respect to electric circuits, and the secondary coils are completely or mostly as well as mutually isolated with respect to electric circuits. By having magnetic circuits completely or mostly as well as mutually isolated, miscellaneous complications resulted from an inverter simultaneously driving two or more light tubes are minimized.
(b) Description of the Prior Art
To have a conventional inverter of a cathode tube simultaneously drive two or more light tubes, two sets (or more) of circuits and two or more transformers are needed. FIG. 1 shows a conventional transformer 100 used in an inverter. Referring to FIG. 1, when driving two or more light tubes, light intensity is not evenly distributed in case of two light tubes in parallel, meaning that currents in the light tubes are unbalanced. As a result, in order to maintain a balance of currents, more electronic components are required, and thus increasing production cost. For light tubes arranged in series, a high output voltage of the transformer from multiplying by the number of the light tubes is required. It is not entirely safe to use such devices, and expenses of related components are similarly increased.
Accompanied with rapid advancement of display technologies, liquid-crystal-display (LCD) monitors are gradually replacing conventional cathode-ray-tube (CRT) monitors for being smaller in thickness, occupying relatively smaller spaces, and having stable definition without flickering. An interior of an LCD monitor is provided with a backlight module, which contains a high-voltage driven cathode tube serving as a light source in a backlight system thereof. This type of light tube is generally driven by an inverter, and has a high-voltage transformer apart from driving circuits. Furthermore, sizes of LCD monitors are currently becoming larger and larger, and some even replace televisions we use at the present time. However, the prior inverter is designed to make a single transformer drive one light tube only, and hence the aforesaid complications are incurred when driving two or more light tubes.